Natural gas, the cleanest-burning hydrocarbon, is a major source of energy. But many energy-hungry places are located far from gas fields, making pipelines too impractical or costly to build. So we offer bulk transport of LNG to such areas.
We are in advanced level of dicussion with a major player in this filed and shall bring these services shortly.
Liquefied natural gas(LNG) is natural gas (predominantly methane, CH4) that has been converted to liquid form for ease of storage or transport. It takes up about 1/600th the volume of natural gas in the gaseous state.
LNG is a clear, colourless and non-toxic liquid which forms when natural gas is cooled to -162ºC (-260ºF). The cooling process shrinks the volume of the gas 600 times, making it easier and safer to store and ship. In its liquid state, LNG will not ignite. When LNG reaches its destination, it is turned back into a gas at regasification plants. It is then piped to homes, businesses and industries where it is burnt for heat or to generate electricity. LNG is now also emerging in India as a cost-competitive and cleaner fuel, especially for shipping heavy-duty road transport.
The heating value depends on the source of gas that is used and the process that is used to liquefy the gas. The range of heating value can span +/- 10 to 15 percent. A typical value of the higher heating value of LNG is approximately 50 MJ/kg or 21,500 Btu/lb. A typical value of the lower heating value of LNG is 45 MJ/kg or 19,350 BTU/lb.
For the purpose of comparison of different fuels the heating value may be expressed in terms of energy per volume which is known as the energy densityexpressed in MJ/liter. The density of LNG is roughly 0.41 kg/liter to 0.5 kg/liter, depending on temperature, pressure, and composition, compared to water at 1.0 kg/liter. Using the median value of 0.45 kg/liter, the typical energy density values are 22.5 MJ/liter (based on higher heating value) or 20.3 MJ/liter (based on lower heating value).
The (volume-based) energy density of LNG is approximately 2.4 times greater than that of CNG which makes it economical to transport natural gas by ship in the form of LNG. The energy density of LNG is comparable to propane and ethanol but is only 60 percent that of diesel and 70 percent that of gasoline.
LNG quality is one of the most important issues in the LNG business. Any gas which does not conform to the agreed specifications in the sale and purchase agreement is regarded as “off-specification” (off-spec) or “off-quality” gas or LNG. Quality regulations serve three purposes:
1. to ensure that the gas distributed is non-corrosive and non-toxic, below the upper limits for H2S, total sulphur, CO2 and Hg content;
2. to guard against the formation of liquids or hydrates in the networks, through maximum water and hydrocarbon dew points;
3. to allow interchangeability of the gases distributed, via limits on the variation range for parameters affecting combustion: content of inert gases, calorific value, Wobbe index, Soot Index, Incomplete Combustion Factor, Yellow Tip Index, etc.
In the case of off-spec gas or LNG the buyer can refuse to accept the gas or LNG and the seller has to pay liquidated damages for the respective off-spec gas volumes.
The quality of gas or LNG is measured at delivery point by using an instrument such as a gas chromatograph.
The most important gas quality concerns involve the sulphur and mercury content and the calorific value. Due to the sensitivity of liquefaction facilities to sulfur and mercury elements, the gas being sent to the liquefaction process shall be accurately refined and tested in order to assure the minimum possible concentration of these two elements before entering the liquefaction plant, hence there is not much concern about them.
However, the main concern is the heating value of gas.
Usually natural gas markets can be divided in three markets in terms of heating value:
1. Asia (Japan, Korea, Taiwan) where gas distributed is rich, with a gross calorific value (GCV) higher than 43 MJ/m3(n), i.e. 1,090 Btu/scf,
2. the UK and the US, where distributed gas is lean, with a GCV usually lower than 42 MJ/m3(n), i.e. 1,065 Btu/scf,
3. Continental Europe, where the acceptable GCV range is quite wide: approx. 39 to 46 MJ/m3(n), i.e. 990 to 1,160 Btu/scf.
There are some methods to modify the heating value of produced LNG to the desired level. For the purpose of increasing the heating value, injecting propane and butane is a solution.
For the purpose of decreasing heating value, nitrogen injecting and extracting butane and propane are proved solutions. Blending with gas or LNG can be a solution; however all of these solutions while theoretically viable can be costly and logistically difficult to manage in large scale.
LNG is rapidly playing a bigger role in the energy mix, and the market for it is expected to grow at around 5% annually. Global demand could increase from about 240 million tonnes per annum (mtpa) to around 430 mtpa in 2025.
For comparison, just 80,000 tonnes of LNG were shipped by two carriers in 1964, the first year of the LNG trade